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Sticking with a global consortium to build the world's largest radio telescope would have committed the Government to making an extra investment in astronomy that it wasn't prepared to.

A briefing from the Ministry of Business, Innovation and Employment (MBIE) to Science and Innovation Minister Megan Woods – dumped just before 5pm this evening – also warned of backlash from those arguing for New Zealand to stay a member of the Square Kilometre Array (SKA) Organisation.

New Zealand was a founding member of the non-profit group and last year downgraded from full membership to associate membership.

But MBIE this week announced that New Zealand would withdraw from the project completely, saying that the benefits of even retaining associate membership in the next construction phase of the project were "not sufficient to account for its cost".

The SKA is being built in the deserts of Australia and South Africa and is expected to be powerful enough to detect very faint radio signals that were emitted billions of light years away from Earth.

It is hoped that the telescope will help answer fundamental questions about the universe, such as how it formed and evolved, the origin of cosmic magnetism, and whether there is life elsewhere in the universe.

The NZ SKA Alliance - a collaboration that included AUT, University of Auckland, Massey University, Nyriad, Catalyst, Open Parallel - had collectively invested up to $10 million, more than twice what the Government had put in to the project.

In the paper released today, officials estimated full membership would have cost between $18m and $25m for the first 10 years – and that they were confident New Zealand could have got most of the critical benefits from being an associate member, likely to cost around $900,000 per year.

However, associate membership had still depended on the willingness of the Government to make "complimentary investments" – and the officials questioned the value of these.

They said that, after Woods announced New Zealand wouldn't be a full member, MBIE had a "series of robust exchanges with stakeholders on our advice, particularly from the ICT sector".

"If anything, those exchanges have left us less convinced of the merits of the investment from an ICT perspective", the officials said, noting that benefits were likely to be captured by a "narrow range" of commercial partners, and that the balance between public and private benefit was "poorly defined" in existing research contracts.

Further, the Government would have had to front up with a further investment in astronomy research – estimated to be in the order of $3m each year, and spread across different fields.

"Any smaller investment would likely be of too small a scale to be effective, but any larger investment would tend to imply too great a priority to astronomy within our broader science investments."

The briefing ultimately recommended that New Zealand not pursue any form of membership, and pay its final contribution - $460,000 – for 2020.

The officials said they were sceptical of claims that the back-out would cause wider reputational damage – and expected to be criticised by a "vocal group of domestic stakeholders".

Nevertheless, they said the call would "require careful management" of communications with the current SKA organisation and international partners.

In a statement this week, AUT Vice-Chancellor Derek McCormack lamented the decision for New Zealand to drop out.

"No current or proposed ICT project comes close to the SKA in scale and opportunity. Its big data demands so greatly exceed those of any other project that the SKA will lead the global development of big data science for years to come," he said.

"Yet, MBIE has advised the Government that continuing with the SKA is not a good idea."

But concerns about the project's value to New Zealand had been spelt out well before this week.

University of Auckland cosmologist Professor Richard Easther previously described the SKA as a "zombie project" that was not welcomed by most astronomers.

Behind-the-scenes tensions spilled into headlines when a Newsroom story detailed how New Zealand SKA Alliance director Dr Andrew Ensor, in an email to technology journalist Peter Griffin, accused Easther of "single handed attempts to destroy NZ's involvement and reputation in the SKA" and suggested that he seek "medical help".

Ensor later emailed Easther to apologise, saying his remark was "clearly inappropriate".

MBIE said that the benefits of New Zealand's participation in the design phase were enduring.

"They include economic development opportunities created within the ICT sector and the strengthening of international relationships as a result of New Zealand's membership in the SKA organisation."

McCormack said some New Zealand radio astronomers would also remain involved, some as full members of SKA working groups, advising design and construction teams.